Some of the key improvements to the smartphone, including a faster quad-core processor and a boost in screen size from 3.5-in. to 4-in., will require significantly more power than the same components in the iPhone 4S, said Shawn Lee, a research director at DisplaySearch.

But rather than thicken the iPhone to accommodate a bigger battery, Apple may instead rely on slimming the display with so-called "in-cell" technology, noted Lee.

In-cell does away with a separate touch-sensitive layer under the glass, and instead integrates sensors into the liquid-crystal display (LCD) itself. By ditching the touch layer, Apple would reduce the thickness of the display module by about half a millimeter, or two-hundredths of an inch.

The iPhone 4S takes the tape at 9.5 millimeters, according to Apple's website.

In a blog post Tuesday, Lee said the thinner display gives Apple more room for a higher-capacity battery, necessary to offset the power-hungry components, including the display itself, and maintain the current time between charges.

"In-cell touch can bring additional benefits [such as] enabling greater battery capacity," said Lee. "We assume that in-cell touch could result in the display module being 0.5 mm thinner, which, combined with battery density of at least 600 Wh/l [Watt-hours per liter], would result in an increase in battery capacity of at least 40% in the iPhone 5."

Talk of Apple using in-cell touch goes back at least to mid- July, when The Wall Street Journal, citing "people familiar with the matter," said the Cupertino, Calif. company would use the technology in the upcoming iPhone 5.

According to The Wall Street Journal, Display Inc., LG Display and Sharp are manufacturing the new displays for Apple.